body {
    background-color: #2b6a98;
    display: flex;
    justify-content: center;
    align-items: center;
    /*给一个body的窗口高度*/
    height: 100vh;
}

.login {
    width: 500px;
    height: 300px;
}

.login > div {
    line-height: 50px;
    height: 50px;
}
.spanRed{
    color: red;
}
.spanGreen{
    color: green;
}